Clive Law dealt with this in his book: the 1st CanadianDivision took something like 80 loose W&S scopes with them when they went to the UK
in 1939/40. Apparently new bases were made up for fitting to P14s, but we don't yet know when and where.
The rifles were still on issue in 1943 and the Canadians took them to Italy, despite their flaws - one of which is on display here: lack of eye relief. The photo is posed and if the rifle was fired as shown the shooter would lose an eye.
One can see from the surviving photos how few No4(T)s had actually been converted (or issued) up to late 1943: the No.4(T)s shown are usually either trials rifles or other early production rifles, and this accords with the inventory of sniping rifles on issue in late 1943. As I recall there were few more No4(T)s than the 1400 trials rifles; the balance was the 421 Alex Martin P14s and the remaining No.3 Mk.I(T) rifles not lost in Francein 1940.
I suspect something happened to interrupt production early on: in later 41 or early 42, wherever it was. That or a decision was taken somewhere in the Ministries to "make do" with what was already on hand "until later". "Later" soon arrived in the form of Italy and then Normandy loomed and suddenly the rush was on?
Meanwhile No.32 Mk.I's cheerfully rolled out in their thousands and went into storage somewhere.